1. Field of the Invention
The present invention relates to a derivatized poly(4-hydroxystyrene) (DPHS) and a process for the production of DPHS indirectly from 4-hydroxymethyl-carbinol (HPMC) and which DPHS has a novolak type structure which has utility in the electronic chemicals market such as photoresist compositions. In addition to the use of DPHS in the microelectronic chemicals market, such DPHS can be employed in standard novolak applications such as varnishes, aniline printing inks, raw materials for epoxy resins (e.g. curing agents) and blocked polyisocyanates, copying paper, tackifiers for rubber, crude oil separators, solder masks and photoimageable coverlays for rigid and flexible printed circuit boards, and further, derivatized epoxy resins and polyisocyanates which have been reacted with the hydroxy groups ofthe DPHS, such as paint formulations containing the same. The DPHS may also be used as a viscosity modifier for highly viscous polymers with the capability of crosslinking after casting and thus providing antioxidation protection therefore.
2. Description of the Prior Art
In the past, one of the ways of preparing poly(4-hydroxystyrene) (PHS) was the use of 4-hydroxystyrene (HSM) as the starting material; note European Patent Application No. 0-108-624. 4-Hydroxystyrene is a well-known compound in the art.
Although there are several known ways to prepare 4-hydroxystyrene, these known methods are not commercially feasible in the further utilization of the 4-hydroxystyrene. The 4-hydroxystyrene itself is difficult to isolate since it (1) readily decomposes, and (2) is toxic via skin absorption and. as a result, those skilled in the art have made numerous attempts at finding a method of synthesizing PHS in a manner which avoids using the 4-hydroxystyrene as the starting material.
The following prior art references are disclosed for informational purposes.
U.S. Pat. No. 5,087,772 (issued Feb. 11, 1992) discloses the preparation of HSM by reacting 4-acetoxystyrene (ASM) with a suitable alcohol in the presence of a catalytic amount of a suitable base.
U.S. Pat. No. 5,340,687 discloses the alkylation of a linear poly(4-hydroxystyrene).
European Patent Application No. 0-128-984 (publication no.) filed Aug. 30, 1983 discloses a process for the production of para-vinyl phenol (HSM) by dehydrogenation of para-ethyl phenol.
European Patent Application No. 0-108-624 (publication no.) filed Nov. 4, 1983, discloses a process for the production of p-vinyl phenol polymer (poly(4-hydroxystyrene) polymer—PHS) by polymerizing p-vinyl (HSM) in the presence of water and iron.
U.S. Pat. No. 4,032,513 (issued Jun. 28, 1977) discloses a process of producing PHS by cationically polymerizing HSM in the presence of a nitrile such as CH3CN using a cationic polymerization initiator in a homogeneous reaction system.
U.S. Pat. No. 5,554,719 and U.S. Pat. No. 5,565,544 disclose a process for preparing a branched PHS directly from HPMC which comprises the single step of polymerizing a mixture of carboxylic acid and at least one substituted phenyl carbinol such as HPMC.
However, it is highly desirable to have a linear DPHS and the prior art does not disclose this, much less a process for preparing the same.
Other prior art references which relate to the present invention include U.S. Pat. Nos. 2,276,138; 3,547,858, 4,544,704; 4,678,843; 4,689,371; 4,822,862; 4,857,601; 4,868,256; 4,877,843; 4,898,916; 4,912,173; 4,962,147; and 4,965,400.
All of the above-cited prior art and any other references mentioned herein are incorporated herein by reference in their entirety.